EP1852722B1 - Cassette for coiling and connecting optical fibres - Google Patents

Abstract

The cassette has a cover closing a rectangular parallelepiped shaped casing (10) in a sealed manner, and a plate (72) delimiting housings (76, 78) that are in the shape of eight. The plate is formed of airproof and waterproof solid material e.g. plastic, that partially fills an empty space inside the casing. The cover has an inner surface covered with an airproof and waterproof solid material layer, where the shape of the layer`s surface conforms to the shape of an inner surface of the casing situated opposite to the cover to partially eliminate the air in the casing when the cover is closed.

Description

The present invention relates to an optical cassette for coiling and / or for connecting optical fibers.

The optical fibers are fragile because of their very small diameter (of the order of a few hundred micrometers) and their structure; they can not therefore be handled without special precautions. First, a number of optical fibers are assembled to form a cable (for example ten fibers), which can be easily used and installed. However, the length of the optical fibers being limited (of the order of a few kilometers maximum) and the distance to travel to convey the information conveyed by the optical fibers is generally greater than this maximum length, it is necessary to connect cables and therefore optical fibers between them. In addition, the optical fiber intended to be connected to a well-defined location (a house or an apartment for example) must be separated from the other fibers of the cable in the vicinity of this location. Cassettes are then used, the main function of which is to protect the optical fibers at these locations of greater fragility of the optical fibers due to the separation and / or the connection of the fibers. These cassettes generally comprise means for covering the optical fibers so as to store the excess lengths of fibers and means for connecting fibers between them. The connection can be made in the form of splices and / or connections using dedicated connectors. A cassette may contain only coiling means or connection means, but it usually contains both. Similarly, although a cassette may relate to only one optical fiber, several optical fibers are processed in a single cassette.

Patent documents WO 2005/088373 or WO 00/03275 disclose an optical cassette comprising a housing containing coiling means and / or optical fiber connection means, at least one input and at least one optical fiber output and a cover sealing the housing. The cassette comprises a plate defining housing and made of a solid material impervious to air and water, the coiling means and / or the means of connecting optical fibers being placed in said housing and said solid material filling at least partially the empty spaces inside the housing.

Several cassettes are generally assigned to the processing of all the fibers of one or more optical cables to be connected. They are stacked in a cabinet or in a box for optical cables and are mounted articulated to have access to each of them, especially for maintenance operations. Cabinets can be placed inside a building sheltered from the weather. Where this is not possible and the cabinets are located outdoors, they are designed to provide some degree of protection, including water. However, variations in temperature, for example between day and night, can lead to moisture condensation in the air, both inside the cabinet and inside the cassettes. This condensation is detrimental to the proper functioning of the optical fibers. Two solutions were then proposed.

A first solution is to place a moisture absorber (a desiccant material) in the cabinet. However, it is necessary to change the desiccant material at least during each re-opening of the envelope / s waterproof / s. A second solution is to increase the thermal inertia of the cabinet and / or cassettes, for example by doubling the wall of the cabinet and / or housings or by increasing the thickness of the walls. This solution is expensive and its effectiveness is limited to not too large temperature variations.

The invention proposes a satisfactory solution to this problem of condensation of the humidity of the air present in the cassettes. A cassette according to the invention can be used individually and externally, exposed to the weather, without the need to be placed in a cabinet. Such a cassette can for example be placed outside a house or a building even when the climatic conditions are relatively severe, as for example in the countries of northern Europe.

More specifically, the invention relates to an optical cassette comprising a housing containing coiling means and / or optical fiber connection means, at least one input and at least one optical fiber output and a cover that closes the housing. sealing manner, cassette comprising a plate defining housing and made of a solid material airtight and water-tight, the coiling means and / or the optical fiber connection means being placed in said housings and said solid material filling at least part of the voids inside the casing, characterized in that the entire inner surface of the lid is covered with a layer of a solid material impervious to water and air, the shape of the surface of said layer projecting inside the housing and conforming substantially to the shape of the surface of the inside of the housing situated opposite the cover, so as to move at least partly the air contained in the housing when the lid is closed.

At the input and / or output of the optical fibers, the latter can be grouped as one or more cable (s).

• lesdits matériaux sont insensibles aux agressions dues à l'environnement.
• lesdits matériaux sont choisis parmi une mousse à cellules fermées, un polyuréthane, un plastique et un silicate.
• des canaux pour le passage des fibres optiques sont délimités par ledit matériau du plateau.
• la cassette comprenant des moyens de lovage ayant au moins un tambour autour duquel peuvent s'enrouler au moins en partie des fibres optiques, le tambour est réalisé dans ledit matériau du plateau.
• l'entrée et la sortie du boîtier comportent chacune des moyens de passage étanche à l'air et à l'eau des fibres optiques et de rétention axiale des fibres optiques.

A cassette according to the invention may comprise one or more of the following characteristics:

• said materials are insensitive to environmental damage.
• said materials are selected from closed cell foam, polyurethane, plastic and silicate.
• channels for the passage of optical fibers are delimited by said tray material.
• the cassette comprising coiling means having at least one drum around which at least some of the optical fibers can be wound, the drum is made in said material of the tray.
• the inlet and outlet of the housing each comprise means for airtight passage and water optical fibers and axial retention of the optical fibers.

• la figure 1 montre en perspective un mode de réalisation d'une cassette optique conforme à l'invention, munie d'un volet en position ouverte;
• la figure 2 montre en perspective le même mode de réalisation que celui représenté sur la figure 1, mais sous un autre angle et avec le volet en position repliée;
• la figure 3 montre en perspective le boîtier de la cassette avec son couvercle, et
• la figure 4 représente en perspective un plateau permettant de diminuer la quantité d'air présent dans la cassette.

Other advantages and characteristics of the invention will become apparent from the following description of several embodiments of the invention, given by way of non-limiting examples, with reference to the appended drawings and in which:

• the figure 1 shows in perspective an embodiment of an optical cassette according to the invention, provided with a shutter in the open position;
• the figure 2 shows in perspective the same embodiment as that shown on the figure 1 but from another angle and with the flap in the folded position;
• the figure 3 shows in perspective the casing of the cassette with its cover, and
• the figure 4 represents in perspective a tray to reduce the amount of air in the cassette.

The cassette shown on the Figures 1 to 3 comprises a housing 10 of substantially rectangular parallelepiped shape and provided with a cover 12 ( figure 3 ). The turn of the housing comprises a shoulder 14 on which can be fixed (by means of screws for example) the cover 12. Sealing means, in the form for example of an O-ring 16 placed on the periphery of the cover 12, make waterproof the air and the closure of the housing 10 by its cover.

Inside the housing 10 are placed coiling means 18 of optical fibers ( figures 1 and 2 ). These coiling means 18 are constituted by two identical drums 20 and 22 which can be fixed to the bottom of the housing, the axis of the drums being substantially perpendicular to the bottom of the housing. The drums are intended to accommodate "8" -shaped optical fibers around the drums. The upper edge of each drum is provided with flat tabs 24 so as to hold the optical fibers on the drums.

The cassette also comprises optical fiber connection means 26, which consist of splice holding means 28 and optical fiber connector support means 30. The means for holding splices 28 can be fixed on the bottom of the housing 10. They consist mainly of ribs between which the splices get stuck. If necessary, they are adapted to receive splices of different types. The connector support means 30 consist mainly of a flap 32 and a connector system 34 ( figure 2 ) The latter is provided with two fixing lugs 36 and 38 rotatably mounted about two axes respectively 40 and 42 fixed on two opposite sides of the housing. The shutter is movable between a fully open position ( figure 1 ) and a folded position ( figure 2 ). For this latter position, the connection system 34 is substantially located above the means for holding the splices 28. The connection system 34 is intended to connect at least two ends of optical fibers each provided with a male-type connector. . The system 34 therefore comprises at least one female type connector for interconnecting two ends of optical fibers.

The housing has an inlet 44 for entering a fiber optic cable 46 (for example based on a tube structure containing a dozen optical fibers of diameter 250 micrometers) in the housing and an output 48 for outputting the individual optical fiber cables 50 of the case. The passage of the cable 46 and the individual cables 50 through respectively the inlet 44 and the outlet 48 is watertight as well as airtight, thanks to the use of a gland. In addition, a seal surrounding the cable is pressed against the cable by a nut which immobilizes the cable. There is therefore both a seal and a retention of the cable (in particular an axial retention in the direction of the axis of the cable).

The cable 46, consisting mainly of the optical fibers 52 surrounded by a protective sheath, enters the housing 10 through the inlet 44. The cable is then stripped and the optical fibers 52 are coiled "8" around the two drums 20 and 22. The purpose of the coiling is to store the excess lengths of optical fibers. The use of at least one drum makes it possible to limit the radius of curvature of the optical fibers to a minimum value below which the optical fibers would no longer function properly and the use of two drums enables reverse the direction of coiling to obtain the "8" shape. The end of each fiber is then welded to the end of an intermediate coupling fiber 54 (called "pigtail" in English), which is an unsheathed bare fiber terminating at its other end by an optical connector 56. thus forms a splice with each optical fiber of the input cable 46. The splices are placed in the splice holding means 28. The intermediate coupling fibers 54 are then coiled around the drums 20 and 22 and the connectors 56 are connected at the inlets 58 of the connection system 34 attached to the flap 32 ( figure 2 ). The outputs 60 of the connector system 34 are connected to the connectors 62 of individual output cables 64. Each of these cables consists of an optical fiber surrounded by at least one protective sheath and provided with a connector 62 (generally male type) at one of its two ends. The connector system 34 makes it easy to make connections and disconnections of the optical fibers. The individual output cables 64 are coiled around the drums 20 and 22, and then exit the housing 10 through the outlet 48 as individual output cables 50.

According to the invention, at least a portion, preferably substantially, of the air normally present in the housing is eliminated so that any condensation of air remaining in the housing is minimal and does not pose a problem for operation. and the integrity of the components in the case. To this end, the space in the housing not occupied by the coiling means 18 and the connecting means 26 is at least partially filled with a material 70 that is airtight and watertight. This material may take the form of a plate 72, one embodiment of which is shown in perspective on the figure 4 . The width and length of the tray are slightly less than the width and length of the housing so that the tray 72 can be inserted into the housing. The cover 12 of the housing ( figure 3 ) is lined on its inner face with a layer 74 of an airtight material and water, this material may be identical to the material 70. The layer 74 is fixed on the underside of the lid for example by gluing . According to one embodiment, the height of the plate 72 added to the height of the layer 74 of the cover is substantially equal to the height of the housing so as to minimize the amount of air remaining in the housing.

The plate 72 comprises housings 76 and 78 in which the coiling means 18 and the means for holding splices 28 are respectively placed. The housing 76, in the form of a "8", has slots 80 and 82 for the drums 20. and 22 a coil and a passage 84, between the locations 80 and 82, for coiling the optical fibers between the drums. According to another embodiment, the drums themselves are shaped in the material 70, the drums thus forming an integral part of the plate 72.

The housing 78 generally accommodates the connection means 26 of the optical fibers. In the particular embodiment described above, with regard to figures 1 and 2 , the connection system 34 is fixed on the flap 32. The plate 72 then comprises a housing 86 for the splice holding means 28 and a housing 88 is arranged in the layer 74 of the lid to accommodate the connector system 34. a conventional configuration cassette, that is to say, in the absence of the flap 32 when the connector system is placed in the housing near the splice holding means, the plate 72 comprises a housing for the connector system 34.

The plate 72 also comprises free spaces or channels 90, 92 and 94 for the passage of the optical fibers respectively from the inlet 44 to the coiling means, from the latter to the means for holding the splices, and the latter to the exit 48.

According to another possible embodiment (not shown), the plate 72 could be thin and have a rim fixed sealingly to air and water on the upper periphery of the housing. The tray would be suspended, either on the edge of the tray (for example on the rim 14), or on an angle fixed on the inner sides of the tray. housing. Air would be present in the lower part of the housing, between the bottom of the housing and the tray. However, because of the tightness of the tray attachment, any condensation of air in this lower part of the housing (between the bottom of the housing and the lower surface of the tray) would have no effect on the components placed in the housing of the housing. tray.

The material 70, in addition to being solid and impervious to water and air, is preferably insensitive to environmental damage, such as for example frost and snow. This is the case when the cassette is intended to be used outdoors, for example in a country where winter conditions are severe. The material may be for example closed cell foam, plastic, polyurethane or silicates. The tray can be for example machined or molded, depending on the material chosen.

the embodiment shown on the figures 1 and 2 comprises coiling means and means for connecting optical fibers. It is obvious that a cassette according to the present invention could comprise only coiling means or optical fiber connection means. In addition, a cassette according to the invention could comprise several inputs and / or several outputs.

Claims (6)

1. An optical cassette comprising a case (10) containing coiling means (18) and/or connection means (26) of optical fibers, at least one optical fiber inlet (44) and at least one optical fiber outlet (48) and a lid (12) sealably closing the case, cassette including a plate (72) defining housings (76, 78) and made of a solid airtight and watertight material (70), the optical fiber coiling and/or connection means being placed in said housings and said solid material at least partially filling the empty spaces inside the case, characterized in that the entire inner surface of the lid (12) is covered with a layer (74) of a solid watertight and airtight material, the surface shape of said layer (74) protruding inside the case and essentially fitting the surface shape of the inside of the case situated opposite the lid, so as to at least partially displace the air contained in the case when the lid is closed.
2. The cassette according to one of claims 1, characterized in that said materials are not sensitive to environmental attacks.
3. The cassette according to claim 1 or 2, characterized in that said materials are chosen among a closed cell foam, a polyurethane, a plastic and a silicate.
4. The cassette according to one of claims 1 to 3, characterized in that channels (92, 94) for the passage of optical fibers are defined by said material of the plate.
5. The cassette according to one of the preceding claims and comprising coiling means (18) having at least one drum (20, 22) around which the optical fibers can be at least partially wound, cassette characterized in that the drum is made in said material of the plate.
6. The cassette according to one of the preceding claims, characterized in that the inlet (44) and the outlet (48) of the case each include airtight and watertight means for passage of the optical fibers and for axial retention of the optical fibers.

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